Unloader for compressors



Aug. 10, 1937. STENGER 2,089,446

UNLOADER FOR COMPRESSOHS Filed May 16, 1935 INVENTOR.

HIS ATTORNEY,

Patented Aug. 10, 1937 PATENT OFFICE 7 2,089,446 UNLOADER FOR COMPRESSORS August M. Stenger, Painted Post, N. Y., assignor to Ingersoll-Rand Company, Jersey City, N. J.,

a corporation of New Jersey Application May 16, 1935, Serial No. 21,726

5 Claims.

-'Ihis.inventionrelates to unloaders, and more particularly to an unloader for air compressors. One object of the invention is to minimize the load on the prime mover of the compressor during the starting period of the compressor.

,Other objects will be in part obvious and in part pointed out hereinafter.

In the drawing accompanying the specification and in which similar reference characters refer to similarparts,

Figure 1 is an elevation, in section, of a compressor equipped with an unloader constructed in accordance with the practice of the invention, and

Figure 2 is an enlarged view, in section, of a detail.

Referring more particularly to the drawing, the compressor 2|] to which the invention is applied comprises a bed plate 2| and a cylinder 22, the latter being bored to form a compression chamber 23 in which is arranged a piston 24. A rod 25 connects the piston to the crank pin 26 of a crank shaft 21 supported by bearings 28 in the bed plate 2|.

The flow of fluid medium to and from the compression chamber 23 is controlled by a valve mechanism of the type illustrated in United States Patent No. 1,986,831 granted January 8, 1935. As in the patent, the valve mechanism forms a closure for the end of the compression chamber 23. It comprises a pair of plates 30 and 3| between which lies a plate 32 of thin material having integral flexible valve fingers 33 and 34.

The finger 33 serves as an inlet valve and controls an inlet port 35 to which fluid medium intended to be compressed is conveyed by an intake conduit 36 connected to the cylinder 22. The plate 3| is provided with a suitable recess 31 to permit the finger 33 to rise freely for admitting pressure fluid into the chamber 31, and communication between the chamber 31 and the compression chamber 23 is afforded by a port 38 in the plate 30.

The finger 34 constitutes a discharge valve. It controls a discharge port 39 through which the compressed fluid passes from the compression chamber into a discharge chamber 40 in the plate 3|, whence it may pass to a point of storage or application through a discharge conduit 4|. A check valve 42 interposed between the discharge chamber 40 and the conduit 4| prevents the return flow of compressed fluid to the discharge chamber 40.

In accordance with the practice of the invention, means are provided to prevent the compression of fluid in the compression chamber 23 and thus the application of a heavy load to the prime mover (not shown) until these .devices have attained a certain pretermined speed. The 5 compressor is accordingly provided with a relief conduit 43 which leads, in the present instance, from the discharge chamber 40 to a point in the base plate 2| substantially coaxial with the crank shaft 21.

As a preferred form of construction the conduit 43 is threaded into a plug 44 which itself is threaded into the base plate 2| and has a recess 45 of which the bottom surface constitutes a seating surface 46 for a valve 41. The valve 41 15 controls a discharge opening 48, in the plug 44, through which pressure fluid may flow from the recess 45 into the interior of the base plate 2|.

The valve 41 is illustrated as being of frustoconical shape. It has a series of longitudinally 20 extending slots 49 in its periphery through which pressure fluid may flow from the recess 45 to the discharge port 48, in the open position of the valve. On the end of the valve confronting the crank shaft 21 is a stem 50 which extends through 25 a bore 5| in the crank shaft and part way into a bore 52 extending longitudinally of a web 53 of the crank shaft.

The bore 52 extends through the axis of the shaft 21. It serves as a guide for a plunger 30 54 which is freely slidable within the bore and has a recess 55 in its outermost end for the reception of a spring 56. The spring acts against the end wall of the bore 52 to urge the plunger 54 in the direction of the stem 55 which extends 35 into the path of the plunger 54. On the innermost end of the plunger 54 is a reduced portion 51 adapted to seat against a stop member 58 threaded into the bore 52.

The operation of the device is as follows: When 40 the compressor is first being started, and at which time the spring 56 predominates over the y centrifugal force acting upon the plunger 54, the plunger will be moved into the plane of the axis of the shaft 21 and pressed against the stop member 58 by the spring 55. In this position of the plunger its inner surface bears against the stem 50 and tilts the valve 41 to the open position illustrated in Figure 2. During the subsequent 50 accelerating period of the compressor the fluid flowing into the compression chamber 23 is expelled into the discharge chamber 40, whence it flows through the conduit 43 into the bed plate 2| and so to the atmosphere or, if desired, 55

through a conduit connecting the interior of the bed plate with the intake conduit 36.

When the speed of the crank shaft 2'! approaches normal the centrifugal force acting upon the plunger 54 will overcome the pressure exerted by the spring 56 and the plunger then moves to the outermost portion of the bore 52 and out of engagement with the stem of the valve 41. The valve 4! will then be free to assume its closed position and will be returned to this position and held there by the pressure fluid flowing through the conduit and acting against the outer surface of the valve. The commpressor will then operate at full load.

I claim:

1. An unloader, comprising means having a passage, a valve to control the. passage, a rotary member, and means encased by the rotary member movable transversely through the axis of the rotary member into and out ofcontact with the valve and acting responsively to the rotary movement of said member for actuating the valve.

2.. An unloader, comprising means having a passage, a valve to control the passage, a rotary member, and means in. the rotary member movable transversely through the axes of the rotary member and the valve to open the valve during the accelerating period, of the rotary member and being normally held inefiective by centrifugal force incident to the operationl of the rotary member.

3. An unloader, comprising means having a passage, a valve to control the passage, a rotary member having a bore extending through the axes of the rotary member and the valve, a stem on the valve extending into the bore, and spring pressed means in the bore adapted to contact the stem for opening the valve during the starting movement of the rotary member and being normally held inefiective by centrifugal force incident to the operation of the rotary member.

4. An unloader, comprising means having a passage, a valve to control the passage, a rotary shaft having a transverse bore, a stem on the valveextending into the bore, a centrifugally actuated plunger in the bore, and a spring to actuate the plunger against the stem for opening. the valve during the starting movement of the shaft.

5. An unloader;com-prising means: having a passage, a valveto control the passageg-a rotary:

shaft, a crank web-on: the shaft having abore arranged perpendicularly to the axis of the shaft,

spring to actuate the: plunger against thestem.

for opening the valve during the starting movement of the shaft.-

AUGUST M. swam. w 

